It is an object of the present invention to provide methods and agents for de-inking printed cellulosic material to produce a pulp that can be handled on conventional paper making machines to produce newsprint, magazine and book stock.
Many methods and compositions are well known to be useful for de-inking printed paper, and the most efficient involve the use of non-ionic surface active agents. Unfortunately, the best non-ionic compounds tend to lack biodegradability and many of them are toxic to marine life, such as fish, making disposal of effluent from such processes a problem. A very broad family of non-ionic agents is disclosed by Lissant, U.S. Pat. No. 3,069,308, to be useful as de-inking agents. Lissant's compounds in their broadest aspects are non-ionic oxyalkylated alcohols. Specifically disclosed by Lissant to be useful are ethoxylated and propoxylated derivatives of lauryl (C.sub.12) alcohol, methoxytripropylene (C.sub.10) glycol, tridecyl (C.sub.13) alcohol, n-butyl (C.sub.4) alcohol, furfuryl (heterocyclic) alcohol, and polyvinyl (polyol) alcohol.
It has now been discovered that within this broad teaching there exists a narrow family of ethoxylated alcohols which are different from the preferred embodiments of Lissant and which provide a very efficient removal of ink and result in paper with excellent brightness and strength. Moreover, the particular agents of this invention have surprisingly been found to be free of toxicity against marine life and are biodegradable, making disposal of process effluents into rivers and streams an acceptable practice.